This invention relates to fluid suction and discharge apparatus including a cylinder block having a plurality of cylinders and pistons slidably reciprocated in the cylinders, for example fluid compressors, and, in particular, to improvements of the seal between adjacent cylinders in such apparatus.
In U.S. Pat. No. 4,011,029, a fluid compressor is disclosed wherein a single sheet of suction reed valve means of a metal sheet comprising a central portion and a plurality of radially outwardly extending reeds is used. The cylinder block is formed with a central spot faced recess on an end surface for the accomodation of the suction reed valve means. A gasket is held between the suction reed valve means and the cylinder block. Thus, the seal between the cylinder block and the valve plate is achieved without the use of a housing to contain the cylinder block and many O-rings so that the volume of the compressor may be reduced.
In the construction disclosed in the prior patent, a narrow gap exists between the peripheral end surface of the central portion of the suction reed valve means and the bent portion of the gasket along the step of the center recess, which communicates between adjacent cylinders.
On the other hand, each reed does not extend to cover the entire sectional area of the corresponding cylinder. Therefore, when the piston reaches the top dead position at the end of the compressing operation, a small part of the fluid is retained in spaces at both sides of the reed between the piston top surface and the valve plate. The retained fluid reexpands in the cylinder at the following suction operation, which results in to a lower volumetric efficiency of the compressor.